title: Endothelial nitric oxide synthase and heme oxygenase-1 act independently in liver ischemic preconditioning.
abstract: BACKGROUND
  ischemic preconditioning (IPC) protects against liver ischemia-reperfusion (IR) injury. The mechanism involves nitric oxide metabolism but the importance of endothelial nitric oxide synthase (eNOS) has not been established. Heme oxygenase-1 (HO-1) protects against liver IR but it is unclear if this depends on nitric oxide synthase.
  
  
  METHODS
  A mouse model of IPC with liver IR using wild-type (WT) and eNOS transgenic knockout (eNOS-/-) mice was developed to study the role of eNOS and its relationship to HO-1. Serum alanine aminotransferase level, liver histopathologic injury scores, and liver microcirculatory blood flow were measured. Western blots measured liver HO-1/2, eNOS, phosphorylated eNOS, inducible nitric oxide synthase, and reverse transcription-polymerase chain reaction (HO-1). A set of 24-h recovery experiments was undertaken on WT mice with measurement of serum alanine aminotransferase level, histologic injury score, and HO-1 by Western blot.
  
  
  RESULTS
  In WT animals, IPC preceding IR resulted in a reduction in hepatocellular and histologic injury, and improvement in parenchymal perfusion. In contrast, IPC in the eNOS-/- model did not protect the animals from IR injury. There was no difference between the eNOS and phosphorylated eNOS expression in all the WT groups. HO-1 protein was not detected in the nonrecovery groups but HO-1 messenger RNA was detected in all groups. In WT recovery experiments, IPC was protective against IR injury. HO-1 protein was detected in the IPC + IR and IR only groups but not in the sham group.
  
  
  CONCLUSIONS
  This study developed and used an eNOS-/- model to demonstrate that eNOS mediates protection against liver IR injury by IPC. The eNOS expression and activity and HO-1 expression are increased independently in liver IPC and IR, with HO-1 expression increased in the later stages of IPC and IR.
authors.affiliation: Division of Surgery and Interventional Science, University College Hospital, London, United Kingdom.
authors.forename: Gourab
authors.initials: G
authors.lastname: Datta
authors.forename: Tu V
authors.initials: TV
authors.lastname: Luong
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Fuller
authors.forename: Brian R
authors.initials: BR
authors.lastname: Davidson
mesh_terms: D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D051547:Heme Oxygenase-1 / Q000502:physiology*; D019194:Ischemic Preconditioning / Q000379:methods*; D008099:Liver / Q000098:blood supply*; D008297:Male; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D052247:Nitric Oxide Synthase Type II / Q000502:physiology; D052250:Nitric Oxide Synthase Type III / Q000502:physiology*; D015427:Reperfusion Injury / Q000517:prevention & control
chemical_list: D008565:Membrane Proteins; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496317:Nos2 protein, mouse; C496315:Nos3 protein, mouse; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; D000410:Alanine Transaminase
keywords: Alanine transaminase; Heme oxygenase; Ischemia; Liver; Microcirculation; Mouse; Nitric oxide synthase; Preconditioning; Reperfusion; Transgenic